The Syrian Observatory for Human Rights on Wednesday said the released school children were part of 150 Kurdish students captured by the IS fighters late last May in Manbej town of the country's northern province of Aleppo, Xinhua reported.
The IS had released a number of kidnapped students before and kept others in captivity under the pretext that their relatives were members of the Kurdish Democratic Union (PYD).
The kidnapped students are from the predominantly Kurdish city of Kobane, also known as Ayn al-Arab, where intense battles have been raging for over a month ago between the IS and Kurdish militants.
Kidnapped students are from the predominantly Kurdish city of Kobane
The observatory spelled no details on the reasons behind the release of the kidnapped students.
The IS unleashed its wide-scale offensive against Kobane Sep 15 in a bid to capture the city, which would enable the Sunni radical group to link its self-declared capital of al-Raqqa province with the Kurdish town and stretch its territory to areas bordering Turkey.
The IS has captured more than 300 villages around the city and managed to storm parts of it after forcing over 160,000 people to flee toward neighbouring Turkey.